Mechanism for an office chair

ABSTRACT

A mechanism for an office chair includes an adjusting device and an electromotive drive used to actuate the adjusting device to simplify manipulation of the adjusting device for changing a movement characteristic of the office chair.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. §119, of GermanPatent Application DE 10 2013 102 008.9, filed Feb. 28, 2013; the priorapplication is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a mechanism for an office chair.

Numerous techniques for changing the movement characteristic of anoffice chair mechanism are known from the prior art. The movement isgenerally a pivoting movement. Depending on the mechanism being used itmay, for example, be a combined synchronous seat/backrest movement or anasynchronous seat/backrest movement. Other movements that are realizableby an office chair mechanism are, for example, the adjustment of theseat inclination independently of the backrest inclination or theadjustment of the backrest inclination independently of the seatinclination.

In that case, an adjusting device for changing the movementcharacteristic of the mechanism frequently includes one or more springconfigurations (for example in the form of a plurality of compression ortension springs connected in parallel) and associated setting mechanisms(worm gears, gear wheels, threaded rods, etc.). If, for example, thepivoting resistance of the backrest of an office chair is intended to bechanged, the tension of the spring elements is usually changed with theaid of a manually operable actuating element, for example a handle orcrank, and thus a setting between “hard” and “soft” is selected,depending on whether the user of the office chair is a heavy or lightperson.

Changing the movement characteristic of the office chair mechanism, inparticular for example the pivoting resistance of the backrest, in thiscase is often associated with the exertion of a comparatively highforce.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a mechanism foran office chair, which overcomes the hereinafore-mentioned disadvantagesof the heretofore-known mechanisms of this general type and whichsimplifies the manipulation of an adjusting device for changing amovement characteristic of an office chair.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a mechanism for an office chair,comprising an adjusting device for changing a movement characteristic ofthe mechanism, in particular for changing a pivoting resistance of abackrest of the office chair, and an electromotive drive configured toactuate the adjusting device.

It is a core concept of the invention to use an electromotive drive toactuate the adjusting device. As a result, the manipulation of theadjusting device is considerably simplified, since manual operation ofan actuating element, associated with the exertion of a comparativelyhigh force, is no longer required. Instead, the user can manipulate theadjusting device without physical effort.

In addition, the use of an electromotive drive for actuating theadjusting device opens up a multiplicity of further options forimproving the office chair mechanism, in particular in connection withchanging the movement characteristic of the mechanism. Thus, themovement characteristic can be adapted, for example automatically andwithout the user being involved, to particular properties of the userand/or to the user's behavior, as is explained in more detail furtherbelow.

In accordance with another feature of the invention, the mechanismincludes an actuating element for actuating the adjusting device. Thisactuating element is connected to the electromotive drive and isdriveable by the electromotive drive. In a very simple case, theactuating element is a spindle. The actuating element is connected tothe drive preferably directly, that is to say without interposition ofan additional component. Complicated setting mechanisms, such as wormgears, gear wheels, threaded rods, etc., are not necessary as a rule.Therefore, the number of components and the manufacturing costs areparticularly low.

In accordance with a further feature of the invention, the adjustingdevice includes a spring configuration having at least one springelement, and the spring configuration is operatively connected to abackrest support of the office chair and determines the pivotingresistance of the backrest support in the event of pivoting from astarting position into a pivoted position. In this case, the actuatingelement is configured to change the tension of the at least one springelement and/or to change the spring rate (also called spring stiffness,spring hardness or spring constant) of the spring configuration.

The spring configuration operatively connected to the backrest supportof the office chair can be connected either directly or indirectly tothe backrest support. In the event of indirect connection, the springconfiguration is connected to the backrest support preferably throughthe seat support as a coupling element. The specific structuralembodiment is dependent on the construction of the office chair and thetype of mechanism (synchronous mechanism, asynchronous mechanism).

The tension of the at least one spring element and/or the spring rate ofthe spring configuration is changed by way of the actuating element, inparticular by way of a change in position of the actuating element, forexample a movement of the actuating element in translation or rotation.For the purposes of the present invention, any desired types of springelement can be used in the spring configuration. Helical springs in theform of leg springs, helical compression springs or helical tensionsprings have proven particularly advantageous due to their simplicityand robustness.

In this case, it is left to the specific configuration of the mechanismas to whether one or more spring elements are tensioned or relaxed whenthe pretensioning of the spring configuration is set. In other words,for example, on one hand a spring element which is completely orpartially relaxed in the unloaded state of the office chair can betensioned in the event of loading, or on the other hand a spring elementwhich is maximally or partially pretensioned in the rest state relaxeswhen the office chair is loaded. However, active forcing of themechanism counter to the movement of the backrest by a number of alreadypretensioned spring elements preferably already takes place even whenthe seat support is not loaded by a user. It is likewise left to thespecific embodiment of the invention as to whether the spring rate ofone or more spring elements is changed and how the change of the springrates takes place.

The pretensioning of individual spring elements and the spring rate ofthe spring configuration can be set fundamentally in two differentmanners. Firstly, it is possible to change the position of at least onespring end of a spring element of the spring configuration with theoverall position of the spring element staying the same or changing.This can take place for example by the spring ends of a helical springbeing pulled apart or pushed together or by rotation or deflection ofone spring leg of a leg spring towards the other spring leg or relativeto the other spring leg, about the spring longitudinal axis extendingthrough the spring midpoint. Secondly, it is possible to change theposition of the spring element itself relative to its fixed or likewiseat least partially movable spring ends. In the case of a leg spring,this can take place for example by displacement of the spring midpointof the leg spring, when the bearing points are fixed. Depending on therequirements placed on the structure of the seat mechanism, bothvariants of spring setting can be realized in the case of the invention.In order to change the spring rate of the spring configuration, it isalso possible for example to change the number of spring elements thatact in the spring configuration.

The invention is not limited to the use of a spring configuration forchanging the movement characteristic. Instead of a spring configuration,the adjusting device for changing the movement characteristic may alsoinclude other components. Thus, for example, instead of a springconfiguration, a variable cam mechanism can be used. What is importantis that the adjusting device or the actuating element of the adjustingdevice is actuated by an electromotive drive.

In a simple embodiment of the invention, the adjusting device isactuated by the electromotive drive in that the drive is operated by theuser, in particular switched on and off. However, an embodiment of theinvention in which the movement characteristic is changed automaticallyand without the user being involved has proved to be particularlyadvantageous.

In accordance with an added feature of the invention, the mechanismpreferably includes at least one measuring device for detecting at leastone user-dependent measured value and also an evaluation and controlunit for evaluating the measurement result and for controlling theelectromotive drive depending on the measurement result. In other words,the electromotive drive of the adjusting device is controlled on thebasis of measured values which are detected in direct temporalconjunction with the use of the office chair. As a result, an individualmovement characteristic, matched to the user, of the office chairmechanism is settable.

For this purpose, in an embodiment of the invention, the evaluation andcontrol unit includes a microcontroller or some other computing unitsuitable for data processing, and a memory in which a characteristiccurve is stored. With the aid of the characteristic curve, particularcontrol values for controlling the adjusting device are assigned topossible measured values. For example, defined spring-force settings areassigned to various user weights. In this case, it may be a conventionallinear characteristic curve or a non-linear characteristic curve. Takingthe actually determined measured values into account, the evaluation andcontrol unit selects, from the characteristic curve defining themovement characteristic of the mechanism, the associated control valuesaccording to which the electromotive drive is subsequently controlled.To this end, a corresponding control signal is generated which causesthe electric motor to move to a position associated with the controlsignal.

In an embodiment of the invention, different characteristic curves arestored in the evaluation and control unit. In this case, it isadvantageous for automatic selection of a characteristic curve which issuitable for the current user or is preferred to take place. A suitablecharacteristic curve is selected for example on the basis of the resultsof the measurements of the measuring device that are taking place. Apreferred characteristic curve is selected for example on the basis ofidentification of the current user. In another variant, the user has thepossibility of selecting a particular characteristic curve.

In accordance with an additional preferred feature of the invention, themeasuring device and the evaluation and control unit are configured tocontinuously measure, evaluate and control. In this case, not onlyuser-individual control of the drive can take place but also continuouscontrol of the drive which is thus matched dynamically to the current,actual loading of the chair. If a plurality of characteristic curves areavailable for selection, it is also possible in this case to change thecharacteristic curve if the evaluation of the measurement resultsreveals that the currently used characteristic curve is providing amovement characteristic which is not optimal for the user.

As an alternative to a continuous mode of operation, the mechanism mayalso be configured in such a way that the setting of the movementcharacteristic, for example the setting of the spring force for pivotingthe backrest, takes place once, when the user sits down on the seat ofthe office chair. The setting is then initiated preferably by theactuation of an operating element by the user, for example by theactuation of a button or the like. However, the one-time setting of themovement characteristic can also be initiated automatically when theuser sits down on the seat.

In accordance with yet another feature of the invention, the at leastone measuring device includes a device for measuring the weight of auser sitting on the office chair.

In accordance with a concomitant feature of the invention, the at leastone measuring device, alternatively or additionally to measuring theweight, includes a device for detecting the weight distribution and/orfor detecting the position of the user on the seat of the office chair.

The selection of the control values, suitable for the user, forcontrolling the electromotive drive with the aid of the characteristiccurve then takes place preferably both with the weight of the user beingtaken into account and with the weight distribution of the user on theseat of the office chair, and thus his or her sitting position, beingtaken into account. In other words, the mechanism is set preferablyautomatically depending on the weight, the weight distribution and/orthe position of the user. As a result, an optimal movementcharacteristic can be selected from ergonomic points of view.

It is particularly advantageous if, in addition to the movementcharacteristic, influenced by the evaluation and control unit, of theoffice chair, selected control values for controlling the electromotivedrive are settable by the user in advance on the chair, or on themechanism, and/or are manually changeable subsequently, or whilesitting. As a result, for example a movement characteristic that isperceived to be uncomfortable can be altered by the user. If the userwishes to operate the electromotive drive and/or the evaluation andcontrol unit, the drive or the evaluation and control unit can beoperated preferably with the aid of suitable operating elements, forexample buttons and/or touch-sensitive surfaces.

The device for measuring the weight of the user is preferably at leastone force sensor or the like, which is advantageously installed underthe seat of the office chair. In order to measure the weight of theuser, it is also possible to provide a plurality of force sensors or thelike that are disposed in a spaced-apart manner.

The device for detecting the weight distribution is preferably a numberof force sensors or the like, which are disposed in a spaced-apartmanner. If both the weight and the weight distribution are intended tobe detected, both devices advantageously make use of the same sensors.

The device for detecting the position of the user is advantageously adevice which has recourse to the measurement data of the weightdistribution and determines the position of the user therefrom. However,the device for detecting the position of the user may also,independently of the force sensors or pressure sensors which may alreadybe present, be a number of touch sensors disposed in or on the seat,wherein these touch sensors react for example to mechanical contactsand/or temperature fluctuations brought about by the user.

In principle, no limits are placed on the type of sensors and measuringdevices that are used. What is important is that the measuring devicesused provide measured values that are dependent on the individual userof the office chair and are relevant for changing the movementcharacteristic of the mechanism in a user-individual manner.

Thus, by way of the invention, a system for changing the movementcharacteristic of an office chair mechanism, in particular for examplefor changing the pivoting resistance of the backrest of an office chair,is created, with the system being set without the user being involvedand differing from the systems known from the prior art in that themovement characteristic, in particular for example the pivotingresistance, is primarily not set arbitrarily by the hand of the user,but automatically and in accordance with the specifications of themechanism, in particular in accordance with the control unit of themechanism and the calculations that take place there or thecharacteristic curves stored there. It is primarily advantageous in thiscase that it is possible to change the movement characteristic, inparticular for example the pivoting resistance, in a particularlysimple, reliable and safe manner. The movement characteristic can, inthis case, not only be set in dependence on the weight of the user butalso in dependence on the sitting behavior of the user.

The invention can be used in numerous office chair mechanisms,irrespective of whether it is a synchronous or asynchronous or someother form of mechanism.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a mechanism for an office chair, it is nevertheless not intended tobe limited to the details shown, since various modifications andstructural changes may be made therein without departing from the spiritof the invention and within the scope and range of equivalents of theclaims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a highly-simplified, kinematic illustration of an office chairmechanism;

FIG. 2 is a more detailed longitudinal-sectional view of an office chairmechanism; and

FIGS. 3-6 are perspective, sectional and elevational views of furtherapplication examples for electromotive drives in office chairmechanisms.

DETAILED DESCRIPTION OF THE INVENTION

Referring now in detail to the figures of the drawings, all of which arediagrammatic, not true to scale and only show important constituentparts and in which identical reference signs correspond to elementshaving an identical or comparable function, and first, particularly, toFIGS. 1 and 2 thereof, there is seen an office chair mechanism 1 havinga base support 2 which is connected to an upper end of a non-illustratedchair column. The mechanism 1 furthermore includes a substantiallyframe-like seat support 3 and a backrest support 4, which is fork-shapedin plan view and has non-illustrated side pieces which are typicallydisposed on either side of the base support 2.

Mounted on the seat support 3 is a seat 10, which is provided with anupholstered sitting surface. Fitted on the backrest support 4 is anon-illustrated backrest, which is height-adjustable in modern officechairs. The backrest can also be connected integrally to the backrestsupport 4.

It is understood that such a description of the mechanism 1 servesmerely to identify the important structural components. A person skilledin the art is familiar with the further structure of an office chairmechanism.

The mechanism 1 includes an adjusting device 6 for changing its movementcharacteristic. An electromotive drive 7 is used to actuate theadjusting device 6. This electromotive drive 7 is, for example, acommercially customary electric motor having a gear mechanism, which isoperated through a mains connection or by batteries or rechargeablebatteries.

The mechanism 1 includes an actuating element in the form of a spindle 8for actuating the adjusting device 6. The spindle 8 is directlyconnected to the electric motor 7 and is driveable by the electric motor7.

The adjusting device 6 includes a spring configuration 5 for forcing themechanism 1 counter to the movement of the backrest support 4. Thespring configuration 5 includes at least one spring element in the formof a compression spring 9. The spring configuration 5 is connectedindirectly to the backrest support 4 of the office chair, with the seatsupport 3 serving as a coupling element. The spring configuration 5determines the pivoting resistance of the backrest support 4. In thiscase, the spindle 8 is configured to change the pretensioning of thecompression spring 9. To this end, the spindle 8 acts directly on aspring seat 11 of the compression spring 9. The spring seat 11 isadjustable in the longitudinal direction of the spring. An oppositespring seat 12 is mounted in a non-movable manner. Thus, a rotation ofthe spindle 8, brought about by the electric motor 7, results in areduction in the distance between the two spring seats 11, 12.

The mechanism 1 includes a measuring device 13 having a plurality ofload cells 13 disposed in a spaced-apart manner beneath the seat, to bemore precise beneath the seat panel, for detecting the weight of theuser. Force transducers can also be used instead of load cells 13.

The mechanism 1 furthermore includes an evaluation and control unit 14for evaluating the measurement results of the measuring device 13 andfor actuating the electric motor 7 in dependence on the measurementresults. In this case, the measured values determined by the load cells13 serve in the evaluation and control unit 14 to simultaneouslydetermine the weight distribution and thus to detect the position of theuser on the seat.

The evaluation and control unit 14 includes a microcontroller 15 and anon-illustrated memory, in which a characteristic curve of the mechanismis stored. This characteristic curve assigns one or more control valuesfor controlling the electric motor 7 to each weight and each sittingposition.

In a simple example, the microcontroller 15 receives an analogue voltagesignal from the load cells 13 and determines therefrom the weight andthe sitting position of the user. Furthermore, the microcontroller 15receives a signal from the electric motor 7 about the current positionof the spindle 8. For this purpose, the electric motor 7 is equippedwith a suitable non-illustrated position sensor. The microcontroller 15contains in its program sequence a characteristic curve which assigns adefined spring force setting to each weight/position combination. Themicrocontroller 15 selects the corresponding control values depending onthe weight and the sitting position of the user. The evaluation andcontrol unit 14 uses these control values to control the electric motor7 and a corresponding control signal is output to the electric motor 7.A suitable control loop causes the electric motor 7 to move into theposition calculated by the microcontroller 15. The measuring, evaluatingand controlling takes place continuously in this case, starting at thetime at which the user sits down on the seat of the office chair.

The load cells 13 or force transducers mentioned in conjunction with thedescribed exemplary embodiment typically use strain gauges to registerelastic component deformations. However, it is also possible to useother suitable sensors. Rather than prefabricated assemblies, the straingauges or other suitable sensors can also be used as individualcomponents. Thus, a strain gauge can be encapsulated, for example, by aplastics seat panel of the seat or a strain gauge is attached to thehousing of the mechanism 1. Individual sensors or assemblies, forexample force transducers, may also be installed between components ofthe chair, as long as such a configuration is suitable for detectinguser-individual measured values, for example between gas spring and basesupport 2 or between gas spring and foot cross.

It is also not necessary for the sensors to be fitted in or on the seatof the office chair. Thus, the weight of the user or a change in thesitting position can, for example, also be detected in that a pressuresensor senses a rise in pressure within a gas spring fitted in the chaircolumn.

In addition to the above-described applications, further applicationsfor an electromotive drive come into question in an office chair.

Thus, for example, a variable travel limitation can be brought about byway of the electromotive drive, as is depicted in FIG. 3. In this case,a pivot angle of the backrest support 4 is limited by an end stop orstop element 22 that is rotatable about an axis 21. This end stop 22 hasa number of steps 23 wherein, by rotation of the end stop 22, in eachcase a different step 23 comes into engagement with a stop surface 24provided on the backrest support 4. The end stop 22 is driveable by aservomotor 25 in such a way that the servomotor 25 can move the end stop22 into these different predefined positions.

FIG. 4 illustrates a structural configuration which can be used toactuate or activate backrest stopping or to limit the travel of anoffice chair mechanism by way of an electromagnetic switch element. Inthis case, two structural elements 26, 27 which are blockable withrespect to one another are used. A connection of the structural elements26, 27 by a pin 28 results, for example, in the stopping of thesynchronous movement function of a synchronous mechanism. For example, amovement of the base support 2 and the seat support 3, the base support2 and the backrest support 4 or the backrest support 4 and the seatsupport 3, is blocked thereby. In order to fix the pin or locking bolts28 in a bistable manner, stationary, spring-loaded ball thrust pieces 29are used. The ball thrust pieces 29 fit in receptacles 30 of a holdingelement 31 connected to the pin 28. A plunger core 32 of anelectromagnet is fitted on the holding element 31 on the side oppositethe pin 28 and coaxially with the pin 28. The plunger core 32 in thiscase is located in the interior of a coil 33 of the electromagnet.Depending on how the electromagnet is controlled, the structural unitcomposed of the plunger core 32, the holding element 31 and the pin 28is moved in the axial direction in such a way that the locking isreleased or re-established.

An electromotive drive can also be used to actuate a gas spring 34 ofthe office chair. FIG. 5 illustrates a variant in which a hexagonalshaft 36 connected to an electric motor 35 engages in an actuatingelement 38 provided with a hexagon socket 37. The actuating element 38is provided with an external thread 39 and is guided in the base support2, which has a threaded bore 40 for this purpose. The base support 2 hasa gas-spring receptacle 41 for receiving the gas spring 34. The threadedbore 40 is positioned in such a way that the actuating element 38 isdisposed directly above a tripping device 42 of the gas spring 34 in afitted state. When the electric motor 35 is controlled, the actuatingelement 38 moves in the direction of the shaft axis towards the trippingdevice 42 of the gas spring 34 or away from the tripping device 42 andthus actuates the latter.

Another variant for actuating a gas spring 34 is depicted in FIG. 6. Inthis case, the tripping device 42 is actuated through a rotatablymounted two-armed control lever 43, which is actuable with the aid of aneccentric disc 44. An electric geared motor 45 is provided to drive theeccentric disc 44.

All of the features illustrated and discussed in the description, thefollowing claims and the drawing can be important to the invention bothindividually and in any desired combination with one another.

1. A mechanism for an office chair, the mechanism comprising: anadjusting device configured to change a movement characteristic of themechanism; and an electromotive drive configured to actuate saidadjusting device.
 2. The mechanism according to claim 1, which furthercomprises a backrest support, said adjusting device configured to changea pivoting resistance of said backrest support.
 3. The mechanismaccording to claim 1, which further comprises an actuating elementconfigured to actuate said adjusting device, said actuating elementindirectly or directly connected to said electromotive drive andconfigured to be driven by said electromotive drive.
 4. The mechanismaccording to claim 3, wherein said actuating element is a spindle. 5.The mechanism according to claim 3, which further comprises: a backrestsupport; said adjusting device including a spring configuration havingat least one spring element; said spring configuration operativelyconnected to said backrest support and configured to determine apivoting resistance of said backrest support in the event of pivotingfrom a starting position into a pivoted position; and said actuatingelement configured to change at least one of a tension of said at leastone spring element or a spring rate of said spring configuration.
 6. Themechanism according to claim 1, which further comprises: at least onemeasuring device configured to detect at least one user-dependentmeasured value and to provide a measurement result; and an evaluationand control unit configured to evaluate said measurement result and tocontrol said electromotive drive in dependence on said measurementresult.
 7. The mechanism according to claim 6, wherein said at least onemeasuring device and said evaluation and control unit are configured tocontinuously measure, evaluate and control.
 8. The mechanism accordingto claim 6, wherein said at least one measuring device includes a devicefor measuring a weight of a user sitting on the office chair.
 9. Themechanism according to claim 6, wherein said at least one measuringdevice includes a device for detecting at least one of a weightdistribution or a position of a user on a seat of the office chair.